If you disagree to agree but agree to disagree, then on are on the same page as me !?
But seriously, the poster is now saying that he wants to grow vegtables in this yard, not a new lawn. That makes your previous answer, and others', right on the money: NO ROUND UP.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!
Roundup, wait a week and till.
Be sure you live your life, because you are a long time dead.-Scottish Proverb
Sometimes the existing "grass" is in such bad shape that a sod cutter will not work well. The original owners of my house had not leveled the ground properly. I could barely mow it! I also had more weeds then grass in the back yard (apparently the builder had graded the front and side yards). I "nuked" the whole area with Round-Up and tilled it under after it was obviously brown and dead. Many weeds can regenerate from live roots. This is another reason to totally kill the weeds before planting anew on top.